Without San Onofre, blackout threat worst in San Diego

San Diego will be most at risk for power outages if the San Onofre nuclear plant remains offline this summer, according to an analysis by state's main grid balancing authority.

To make up for possible lost generation at San Onofre, the region's largest power plant, the electrical system operator has proposing to restarting two gas-fired generation units at Huntington Beach. That would restore some electrical generation -- and a substantial loss of import capacity along a transfer corridor into San Diego that San Onofre helped sustain through its relative weight on the grid.

The analysis was presented Thursday to the board of the California Independent Service Operator, which balances supply and demand across most of the state's transmission grid. It found San Diego would be especially vulnerable to blackouts if there is heavy demand for electricity this summer.

San Onofre ordinarily provides up to 2,240 megawatts of electricity, enough to power about 1.4 million homes. But the seaside, dual reactor facility 45 miles north of San Diego remains offline indefinitely as plant operator Southern California Edison searches for the root cause of a steam generator tube rupture at one reactor and accelerated wear on tubes at both units.

"We have risk with the San Onofre plant being down this summer," said Steven Berberich, president and chief executive officer of the California ISO. "There is significant risk if in fact we have heavy loads down there and there are other contingencies on the system."

Activating the Huntington Beach units should boost imports just enough to meet demand during a period of heavy summer demand within San Diego Gas & Electric territory, according to an analysis presented by Neil Millar, executive director of infrastructure development at the ISO.

"We're studying the impact of that generation on the ability to support the transfer path into that area," said Millar. "Even under the most severe conditions, the system would remain stable."

The system operator is pursuing several other measures to keep operating margins for electricity over the 3 percent margin where blackouts ensue. They include:

Accelerating transmission upgrades and the completion of the Sunrise Powerlink transmission line running east from San Diego.

Seeking additional reductions in electricity use from the military and public agencies.

Fully utilizing voluntary service cutbacks and interruptions built into tariffs or contracts.

Funding advertizements on radio and TV appealing to the public to conserve energy.

Boosting electricity production at crucial points by contracting large mobile generators.

San Onofre hasn’t produced any electricity since Jan. 31 when a generator steam tube rupture was detected at its southern reactor.

A special team of inspectors from the Nuclear Regulatory Commission is on site as Edison performs pressure tests on more than 100 generator tubes, part of a mildly radioactive steam loop that circulates through the reactor core.